Provides a CAPTCHA for Python using the reCAPTCHA service. Does not
require any imaging libraries because the CAPTCHA is served directly
from reCAPTCHA.  Also allows you to securely obfuscate emails with
Mailhide. This functionality requires pycrypto. This library requires
two types of API keys. If you'd like to use the CAPTCHA, you'll need a
key from https://www.google.com/recaptcha/admin/create.  For Mailhide,
you'll need a key from http://www.google.com/recaptcha/mailhide/apikey.
